COVID-19 | Sanofi and GlaxoSmithKline said clinical trials of their Covid-19 vaccine showed an insufficient immune response in older people, delaying its launch to late next year and marking a setback in the global fight against the pandemic.

The announcement on Friday, which highlighted the challenges of developing shots at record speed, hinders efforts to develop the multiple options that experts say the world needs to counter a disease that has killed over 1.5 million people...